Modulated 3D Cross-Correlation Light Scattering

 
 

One drawback of the 3D cross-correlation technique is that one photon detector measures the scattered light intensity at the desired scattering vector, but also receives a contribution at a second undesired scattering vector given by the relative geometry to the second illumination beam operating at the same wavelength.  A four-fold reduction in the cross-correlation intercept arises from cross-talk between the two simultaneous scattering experiments executed in this way.  The correlation intercept strongly influences measurement accuracy and precision due to its pivotal role in accurately fitting models to the measured data.  For strongly scattering samples where only a small component of the detected light is singly-scattered, the signal-to-noise ratio of the measurement becomes unacceptably low as the magnitude of the cross-correlation intercept falls into the noise of the baseline fluctuations.

 

The new modulated cross-correlation unit for static and dynamic light scattering is now available from LS Instruments.

 
 

In order to circumvent this limitation, we have recently demonstrated a method in which the two scattering experiments are temporally separated by modulating the incident laser beams and gating the detector outputs at frequencies exceeding the timescale of the system dynamics.  This robust modulation scheme eliminates cross-talk between the two beam-detector pairs and leads to a four-fold improvement in the cross-correlation intercept, while fully suppressing the negative effects of multiple scattering.

 

Modulated cross-correlation technology efficiently suppress multiple scattering in static and dynamic light scattering without with nearly no loss in signal quality.  

 
 

False measurement due to multiple scattering cannot be avoided when using simple auto-correlation. They result in significant errors in both SLS and DLS measurements, often without ever being noticed.


The modulated cross-correlation technology is now available as an upgrade for the 3D LS Spectrometer.


We invite you to read more about this exciting development in our recently accepted publication in the American Institute of Physics' well-regarded Review of Scientific Instruments. 

 

 


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